Process of treating water



Reissued Ma 11, 1937 UNITED-STATES PATENT OFFICE rnocnss or TREATING ws'raa Ludwig Rosenstein, San Francisco, Calif assignor .to Shell Development Company. San Francisco,

Calii., a corporation oi Delaware 10 Claims.

. This invention relates to a process for avoiding the deposition of calcium carbonate from natural waters at their natural temperatures.

This invention is particularly useful where ferti- I 26 The precipitates so formed from natural waters also contain magnesium carbonate. To avoid repetition the termcalcium"will be used throughout this specification whenever both calcium and magnesium compounds are'intended. I

25 The precipitation of calcium carbonate is the factor which limitsthe amount of ammonia which can be added to the water. For example, with a particular irrigation water (applied to an orange grove) having a calcium concentration of one! 30 hundred and twenty parts per million of water and nearly the equivalent amount of bicarbonate, it was found that the ammonia passed into the water had to be limited to twelve and one-half pounds per hour when water was applied at the 5 rate of 225,000 lbs/hr. Any larger introduction of ammonia resulted in the fatal plugging of the *pipe lines, valves and the like, due to the heavy precipitation of calcium carbonate. Application of ammonia at the above low rate was totally inadeguate to supply the needs oi the orange trees. In order to overcome this-difliculty 4 in this and similar cases, it was necessary to devise some means of either preventing the precipitation of calcium carbonate or inhibiting itsformation tor a suilicient time period so that all water would leave the system beioreprecipitation took place, or causing the precipitated particles to be of such physical character that they would be swept out oi the by the ilow of water and would not mssuw deposit on the surfaces 01 the pipes and valves forming the distribution system.

It is an object of this invention to devise a method of preventing the deposition of calcium carbonate iromwaters. It is a further object of 5 this invention to devise a process which will enable ammonia to be added to irrigation water in greater quantities than heretofore.

It is another object of this invention to devise means which will avoid deposition oi calcium car- 1 bonate produced by the addition of ammonia to water. i I

In brief, my invention comprises the addition of substances to water which will avoid or delay the precipitation of calcium carbonate or will pro-' duce such precipitate in so finely divided a state that it will not adhere tothe pipes and valves through whichthe water is passed. 1 i

The following is an example of the use of a precipitation retarding colloid. A hay infusion was madeby steeping 100 grams of alfalfa hay in one liter 01' water and allowing the hay to remain until bacterial action had progressed to aconsiderable degree. The liquid containing the infusion was drained oil? and added in the amount of. one cubic inch of liquid to one hundred cubic inches of irrigation water containing calcium bicarbonate in large amounts. After the addition of ammonia to the water it wasiound that the precipitation of calcium carbonate was delayed ior approximately twenty minutes. The precipitate ultimately formed was very fine andnonadherent.

I have found that certain chemicals when added to the water will also retard the precipitation and render the precipitate finely divided and nonadherent.

The following is an example of these latter compositions. To a watercontaining 142 parts per million of calcium ion, ammonium hexa-meta phosphate was added so as to produce a meta phosphate concentration oi from 0.50 part per million to 1 part per million. Thereafter sufficient ammonia was added into the water to produce an ammonia concentration of 500'parts per million. This would normally cause the rapid precipitation 01- large amounts, of calcium carbonate. No precipitation took placei'or several hours. Instead of ammonium meta phosphates I may use other meta phosphates such as sodium meta phosphates, potassium meta phosphates or I may use meta phosphoric acid.

A significant part of this discovery is the very small amount of the reagent required. It is well known for example, that sodium hexa meta phosphate will react with calcium'ions in water'to form complex ions so that insoluble calcium compounds such as calcium soaps and calcium'carbonate not formed. The complex ion containing the largest amount of calcium is known to be I have found that it is not necessary to combine all the calcium into the complex ion 3); F and that precipitation of the calcium may be inhibited by using quantities of reagent far below the stoichiometric amount.

According ,to my discovery 1/2000 to 1/1000 of this stoichiometric amount is suflicient to accomplish the desired result when sodium hexa metaphosphate, potassium hexa metaphosphate or ammonium hexa metaphosphate are used.

It should be understood that in this speciflca-' tion and in the claims attached hereto, the term .alkali-metal" includes ammonium. I

I have also found that other soluble phosphates have the property of affecting the precipitation of calcium carbonate. For example, so- 0 dium pyrophosphate, orthophosphoric acid and in general salts of orthophosphoric acid all display the efl'ect of delaying the precipitation of .insoluble calcium compounds or of afl'ecting their physical character so that the precipitate is finely divided and non-adherent.

Other organic colloidal substances such as for 1 example, tannic acid, bark'extracts, manure infusion and the like also effect the rate of precipitation and physical character of the precipitat'e favorably for the objective desired.

The treating reagent can be added to the water by any suitable metering device. F

Where ammonia is added to the irrigationwater from cylinders of anhydrous ammonia, amoimts 55 of treating reagent can be added to the water at the same time and in proportion to the ammonia flow by well known devices. It is preferable in the case of meta phosphate or metaphosphorlc acid that it be introduced into the water at a point upstream from ,the point of ammonia iniection.

I claim as my invention: 1. Process of retarding the precipitation of calcium carbonate from natural waters compris- 55 ing adding to the water an all-metal hexa meta phosphate in amounts ot exceeding one thousandth part of the'stoichiometric amount required to react with said calcium to form calcium metaphosphate whereby precipitation 70. of calcium carbonate resulting from the addition of alkali is prevented. I

2. In a process of supplying increased amounts of fertilizer to soils by means of irrigation water, the step of adding a calcium carbonate precipitation retardant to said water in amounts only sumcient to prevent the precipitation of calcium carbonate upon the subsequent addition of amthereafter passing ammonia into said water and supplying said treated water tothe soil.

5. Process. for inhibiting in natural waters the precipitation of calcium carbonateresulting from the addition of alkali consisting in adding to the watenan alkali-metal hexa meta phosphate in substantially less than. stoichiometricamounts.

6. Process for inhibiting in natural waters the precipitation of calcium carbonate resulting from an'increase in carbonate ion concentration consisting inadding to the water an alkali-metal hexa meta phosphate in substantially less than stoichiometric amounts.

7. Process for supplying increased amounts of fertilizer .to soils by means of irrigation water comprising adding a calcium carbonate precipitation retardant to water in an amount sumcient to prevent the precipitation of calcium carbonate from said water upon the subsequent addition of ammonia. adding ammonia to ,said water, thereaftersupplying said treated water to the soil fertilizer to soils by means of irrigation water comprising adding a soluble phosphate to said 7 water in'amounts suflicient to prevent the precipitation of calcium carbonate from said water upon the subsequent addition of ammonia, adding ammonia to said water, thereafter treated waterv to the soil. a

9. Process for supplying increased amounts of fertilizer to soils by means of irrigation water comprising adding a soluble meta phosphate to water inamounts sufficient to prevent the precipitation of calcium carbonate upon the subsequent addition of ammonia, adding ammonia to said water thereafter supplying said treated watertothesoil.

10. Process for supplying increased amounts of fertilizer to soils by'means of irrigation'water comprising adding a member of the group'fcons'isting of ammonium meta phosphate, sodium meta'phosphate. potassium meta phosph te and meta phosphoric acid to water in amounts sufficient to prevent the precipitation of calcium carbonate upon the subsequent addition of ammonia ,.adding ammonia to said water thereafter supplying said treated water to the soil.

puma :i! I

. Process for supplying increased amounts of supplying said 

